2017 ISAKOS Biennial Congress ePoster #325

 

Biceps Tenodesis: A Comparison of Tendon-to-Bone and Tendon-to-Tendon Healing in a Rat Model

Ekaterina Urch, MD, Santa Monica, CA UNITED STATES
KERRY LEE ESCOBAR, MD, Harrison, NY UNITED STATES
Prem N Ramkumar, MD, MBA, Cleveland, Ohio UNITED STATES
Stephen B Doty, PhD, New York, NY UNITED STATES
Alexander Earle White, BA, New York, NY UNITED STATES
Demetris Delos, MD, Greenwich, CT UNITED STATES
Mary E. Shorey, BA, New York, NY UNITED STATES
Stephen James O'Brien, MD, MBA, New York, NY UNITED STATES

Hospital for Special Surgery, New York City, New York, UNITED STATES

FDA Status Not Applicable

Summary

Biceps tenodesis using a tendon-to-tendon transfer method optimizes healing and minimizes the inflammatory response when compared with metaphyseal or diaphyseal tenodesis techniques in a rat model.

Abstract

Introduction

Histological analysis of three common biceps tenodesis sites (metaphyseal, diaphyseal, conjoint tendon) revealed two different healing processes in this basic science study using a rat model. Bony tenodeses healed with an inflammatory degenerative response, while tendon-to-tendon tenodesis demonstrated a quieter regenerative healing pattern. Tendon-to-tendon tenodesis appears to optimize healing and minimize inflammatory response when compared with the two tendon-to-bone techniques.

Methods

The long head of the biceps (LHB) was tenodesed in 36 13-week old Sprague-Dawley rats to three different locations. Metaphyseal (MT; n=12) and diaphyseal (DT; n=12) tenodeses were performed by passing the LHB through a transosseous drill hole and securing with an inert suture. Tendon-to-tendon tenodeses (TT; n=12) were performed by securing the LHB to the conjoint tendon with the same inert suture. Animals were not immobilized post-procedure. Four animals from each group were sacrificed at 6-, 12-, and 24-weeks after surgery. Specimens were formalin fixed, decalcified in 10% EDTA, and paraffin embedded. Sections were stained with hematoxylin and eosin (H&E), CD68 (macrophage marker), and tenomodulin (Tnmd; tenocyte marker). Overall cellularity was quantified on the H&E slides by averaging the nuclei count within 3 separate 20x magnification high power fields (HPF) at the tenodesis interface (tendon-to-bone or tendon-to-tendon). Inflammatory response was measured in an identical fashion by averaging the number of CD68 positive cells per HPF. The presence of tendon cells at the tenodesis interface was evaluated based on the presence or absence of a positive Tnmd reaction.

Results

Cellularity was significantly higher in the MT and DT groups at 6-weeks (MT: p=0.012; DT: p=0.021) and 12-weeks (MT: p=0.002; DT: p=0.001) when compared to the TT group. There was no difference in cellularity between the MT and DT groups at any of the time points. The macrophage response was significantly more robust in the MT and DT groups than the TT group at both 6-weeks (p<0.001 for both) and 12-weeks (MT: p=0.002; DT: p<0.001). (Figure 1a) No difference in CD68 reaction was seen between the groups at 24-weeks. The TT group had a strongly-positive Tnmd reaction at both 6- and 12-weeks. (Figure 1b) Tnmd reaction was absent in the MT and DT groups at all three time points. In all cases of tendon-to-bone tenodesis, no recognizable formed tendon was seen within the bone tunnel. Rather, all tendon-to-bone tenodeses were characterized by dense connective tissue at the bone surface, surrounded by a large accumulation of macrophages.

Discussion

Tendon-to-bone tenodesis (both metaphyseal and diaphyseal) produced a significantly greater inflammatory response at the tenodesis interface than did soft tissue-to-soft tissue tendon fixation at both the 6- and 12-week time points. Tendon-to-tendon tenodesis limits the inflammatory response and optimizes healing. The presence of a robust Tnmd reaction in the early healing stages in this group suggests a regenerative healing process. Macrophage proliferation within the bone tunnel in the setting of absent formed tendon suggests tendon degeneration and calls into question the rationale behind tunnel fixation.